<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin:0;
            padding:0;
        }
        div{
            height:300px;
            width: 500px;
            background-color: aquamarine;
            margin:200px;
            /* padding-top:200px; */
            
            /* transparent 透明色 */
            /* border-top:1px solid transparent; */
            /* overflow: hidden; */
        }
        p{
            height:200px;
            width: 200px;
            background-color: blue;
            /* margin 有穿透问题 
              1. 给父级盒子添加边框
              2. *****给父级盒子添加 overflow: hidden;
            */
            /* margin-top:200px; */
        }
    </style>
</head>
<body>
    <div>
        <p></p>
    </div>
</body>
</html>